Admixtures are known in the art as materials used as ingredients in cementitious compositions to modify some property or properties of the cementitious compositions before, during or after the cementitious compositions have been formulated. Set retarding agents, accelerators, water reducers, superplasticizers and air-entraining agents are typical admixtures commonly used in the industry.
The successful use of admixtures depends in part upon the amount used for any given batch of cementitious mixture. Excess or insufficient amounts added to the mix may deleteriously affect the properties of the mix, and often result in considerable waste, not only of the admixture proper, but of the improperly dosed mix as well.
Conventional techniques for dispensing semi-fluid admixtures into cementitious compositions generally require extensive apparatus, which is costly, time-consuming and labor-intensive. In addition, use of such apparatus can result in spills, the generation of fumes, and may result in workers physically contracting the admixture, which can be undesirable. Most materials used as admixtures for cementitious mixtures are in aqueous, highly fluid states or in solid or powdered states. Semi-fluid admixture materials that have high viscosity at temperatures of 30.degree.-100.degree. F. are especially difficult to dispense into cementitious mixtures. One mechanism for metering such admixtures is a bulk blending station including bulk tanks, pump motors, electromagnetic meters, calibrated sight vessels, and necessary hoses.
In the case of solid or powdered admixtures, typically the dispensing involves manually introducing loose admixtures into the cementitious mixture by mass or volumetric measurement. Another device involves water-soluble containers that envelop solid or powdered material, and the containers dissolve and release their contents while being blended into the wet cementitious mixture. For example, U.S. Pat. No. 4,961,790 to Smith et al. discloses a device comprising a solid or powdered concrete admixture contained in a water-soluble container. When the container is introduced into a wet mixer and agitated, the water-soluble container is dissolved and the contents are thereby released into the mixer.
However, there is currently no viable packaging and dispensing technique for concrete admixtures that address the problem of dispensing admixtures that are in a semi-fluid or fluid state into cementitious mixtures without the use of extensive apparatus, or without the high probability that admixtures may spill in transit.